A 45–year–old man presented with vertebral collapse at L5 as an initial manifestation of multiple myeloma and underwent spinal fusion surgery using recombinant human bone morphogenetic protein–2. Subsequent computed tomography scans and X–rays revealed heterotopic ossification of the left psoas muscle, pelvis, and anterior abdominal wall. While the occurrence of heterotopic ossification has previously been reported when rhBMP–2 has been used for spinal fusion surgery, this case demonstrates that it can occur to a much greater degree than previously seen.